| 1 | D & P Operating & Prod. Corp. | Cedar Park, TX 78613 | Oil & Gas Operator | Dec 2003 |
| 2 | Dalen Resources Oil & Gas Co. | Dallas, TX 75206 | Oil & Gas Operator | Jun 2010 |
| 3 | Dallas Operating Corp. | Dallas, TX 75205 | Oil & Gas Operator | Nov 2006 |
| 4 | Daniels Corporation, The | Seabrook, TX 77586 | Oil & Gas Operator | Oct 2025 |
| 5 | Dantex Oil & Gas, Inc. | Dallas, TX 75225 | Oil & Gas Operator | Aug 2003 |
| 6 | Dartex Energy Corporation | Austin, TX 78746 | Oil & Gas Operator | Oct 2025 |
| 7 | Davis Bros. Oil Producers, Inc. | Tulsa, OK 74119 | Oil & Gas Operator | Apr 2020 |
| 8 | Davis Energy Services LLC | La Grange, TX 78945 | Oil Operator | Oct 2025 |
| 9 | Davis Gulf Coast, Inc. | Tulsa, OK 74103 | Oil & Gas Operator | Oct 2025 |
| 10 | Davis Operating Company | Elysian Field, TX 75642 | Oil & Gas Operator | Oct 2025 |
| 11 | Davis Southern Operating Co LLC | Houston, TX 77004 | Oil & Gas Operator | Oct 2025 |
| 12 | Daylight Petroleum LLC | Houston, TX 77052 | Oil & Gas Operator | Oct 2025 |
| 13 | Daystar Operating Company, LLC | Austin, TX 78750 | Oil & Gas Operator | Apr 2008 |
| 14 | Deguello Operating LLC | Kilgore, TX 75663 | Oil & Gas Operator | Oct 2025 |
| 15 | Delaware Davis Petroleum Corp. | Houston, TX 77056 | Oil & Gas Operator | Jan 2000 |
| 16 | Delco Operating Company LP | Houston, TX 77056 | Oil & Gas Operator | May 2020 |
| 17 | Delta Exploration Company Inc | Denver, CO 80202 | Oil & Gas Operator | Oct 2025 |
| 18 | Delta Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Dec 2024 |
| 19 | Denbury Onshore, LLC | Plano, TX 75024 | Oil & Gas Operator | Oct 2025 |
| 20 | Denovo Oil & Gas, Inc. | Houston, TX 77210 | Oil & Gas Operator | May 1995 |
| 21 | Derrick Oil & Gas, Inc. | Rosharon, TX 77583 | Oil & Gas Operator | Aug 2003 |
| 22 | Devon Energy Production Company LP | Oklahoma City, OK 73102 | Oil & Gas Operator | Oct 2025 |
| 23 | Dewbre Petroleum Corporation | Corpus Chrsti, TX 78404 | Oil & Gas Operator | Oct 2025 |
| 24 | Dorado Oil Company | Corpus Chrsti, TX 78403 | Oil & Gas Operator | Oct 2013 |
| 25 | Drillmar Energy, Inc. | Houston, TX 77079 | Oil & Gas Operator | Nov 2014 |
| 26 | Drillmar Operating Company | Houston, TX 77019 | Oil & Gas Operator | Jun 2013 |
| 27 | Driscoll S.W.D. Inc. | San Antonio, TX 78229 | Oil & Gas Operator | Oct 2025 |
| 28 | Duncan Energy Company | Denver, CO 80202 | Oil & Gas Operator | Mar 2008 |
| 29 | Duncan Oil Inc | Denver, CO 80210 | Oil & Gas Operator | Jun 2016 |
| 30 | Dune Operating Company | Dallas, TX 75201 | Oil & Gas Operator | Jun 2016 |